Efficient sharing of a continuous-variable quantum secret

We propose an efficient scheme for sharing a continuous variable quantum secret using passive optical interferometry and squeezers: this efficiency is achieved by showing that a maximum of two squeezers is required to replicate the secret state, and we obtain the cheapest configuration in terms of total squeezing cost. Squeezing is a cost for the dealer of the secret as well as for the receivers, and we quantify limitations to the fidelity of the replicated secret state in terms of the squeezing employed by the dealer.Comment: 7 pages, 3 figure

An omnidirectional retroreflector based on the transmutation of dielectric singularities

In the field of transformation optics, metamaterials mimic the effect of coordinate transformations on electromagnetic waves, creating the illusion that the waves are propagating through a virtual space. Transforming space by appropriately designed materials makes devices possible that have been deemed impossible. In particular, transformation optics has led to the demonstration of invisibility cloaking for microwaves, surface plasmons and infrared light. Here we report the achievement of another "impossible task". We implement, for microwaves, a device that would normally require a dielectric singularity, an infinity in the refractive index. We transmute a singularity in virtual space into a mere topological defect in a real metamaterial. In particular, we demonstrate an omnidirectional retroreflector, a device for faithfully reflecting images and for creating high visibility, from all directions. Our method is robust, potentially broadband and similar techniques could be applied for visible light

No approximate complex fermion coherent states

Whereas boson coherent states with complex parametrization provide an elegant, and intuitive representation, there is no counterpart for fermions using complex parametrization. However, a complex parametrization provides a valuable way to describe amplitude and phase of a coherent beam. Thus we pose the question of whether a fermionic beam can be described, even approximately, by a complex-parametrized coherent state and define, in a natural way, approximate complex-parametrized fermion coherent states. Then we identify four appealing properties of boson coherent states (eigenstate of annihilation operator, displaced vacuum state, preservation of product states under linear coupling, and factorization of correlators) and show that these approximate complex fermion coherent states fail all four criteria. The inapplicability of complex parametrization supports the use of Grassman algebras as an appropriate alternative.Comment: Argumentation made cleare

George Champlain Sibley: Shady Dealings on the Early Frontier

Danisi offers an analysis of Sibley’s time as assistant factor at Fort Bellefontaine under factor Rodolphe Tillier, a man of strong political connections and elastic ethics. Tillier fired Sibley, Danisi argues, because he discovered and revealed Tillier’s shady business dealings while a government official; ultimately, Sibley was exonerated and even promoted to factor of the newly formed Fort Osage

Hoyle state and rotational features in Carbon-12 within a no-core shell model framework

By using only a fraction of the model space extended beyond current no-core shell-model limits and a schematic effective many-nucleon interaction, we gain additional insight within a symmetry-guided shell-model framework, into the many-body dynamics that gives rise to the ground state rotational band together with phenomena tied to alpha-clustering substructures in the low-lying states in C-12, and in particular, the challenging Hoyle state and its first 2+ excitation. For these states, we offer a novel perspective emerging out of no-core shell-model considerations, including a discussion of associated nuclear shapes and matter radii. This, in turn, provides guidance for ab initio shell models by informing key features of nuclear structure and the interaction.Comment: 5 pages, 4 figure